Mold core



Aug. 6, 1946.

R. K. HOPKINS MOLD CORE Filed Marqh '2, 1943 INVENTOR Wk. BY

- ATTORNEY Patented Aug. 6, 1946 MOLD CORE Robert KHopkins, New York, N.Y., assignor to The M. W.

Kellogg Company,

New York, N. Y

a corporation of Delaware Application March 2, 1943, Serial No. 477,7384 Claims. (01. 22 17c) The present invention relates to molds, and moreparticularly to cores for shaping the interior of hollow castings.

In castin hollow objects the use of a metal core is often desirable,particularly because of its durability. However, shrinkage of the castmetal makes removal of the core diiiicult, and will usually producesuflicient strain in said core to permanently deform it and render itunserviceable for further use.

One object of the present invention is to provide a new and improvedmetal core which can be easily removed from a casting, and which willnot be permanently upset or deformed by the shrinkage pressure of thecasting thereon.

As a feature of the present invention, the core is of sectionalconstruction and is collapsible into a smaller cross-section uponapplication of shrinkage pressure thereon.

As a further feature, the sections of the core are automaticallyrestored to expanded condition when the shrinkage pressure is removed.

As another feature, the different sections of the core are hollowed topermit circulation of a cooling liquid therethrough.

Various other objects, features and advantages of the invention will beapparent from the following particular description, and from aninspection of the accompanyin drawing, in which Fig. 1 is a verticalsection, somewhat diagrammatic, through a casting apparatus containing acore which embodies one form of the present inventicn;

Fig. 2 is a transverse section of the core taken on line 2-2 of Fig. 1;and

Fig. 3 is a transverse section of another form of core embodying thepresent invention.

Referring to Figs. 1 and 2 of the drawing, the core Iii comprises aseries of similar segments H, three being shown, separated by wedges 12.These core sections I l and 42 are desirably made of metal having highheat conductivity such as copper. Each of the core segments H ha anouter circular conformation i3 and an inner chordal surface itintersecting said circular conformation and slidably seating the wedgesl2. The wedges [2 are approximately trapezoidal in cross-sectionaloutline with respective outer cir cular conformation l5 formingcontinuations of the segment conformations l3 in expanded condition ofthe core shown in Fig. 2. Each wedge l2 has a base it extending betweenthe two chordal surfaces M of respective flanking segments l l, andopposed inclined plane surfaces l7 slidably engaging said chordalsurfaces respec- 2 tively. The angle betwe n these inclined wedgesurfaces l1 and the coeficient of friction between the contactingsurfaces of the wedges I2 and the segments H are such that uponapplication of radially inward pressure on the segments H resulting fromshrink pressure the wedges l2 slip radially inwardly along the innersurfaces [4 of said segments. This radially inward sliding of the wedgesl2 causes collapsible approachment of the segments H, and resultantreduction in the diameter of the core I 0.

The core sections I I and I2 are normally maintained in expandedposition shown in Fig. 2 by resilient means comprising radiallyextending coil springs 29, retained at their inner ends in respectiverecesses 2| of a block 22 which is set in the interior of the core l0,and which may be of metal as shown or of suitable refractory material.The outer ends of these coil springs 20 bear against the bases it of thewedges [2 to urge these wedges radially outwardly. Three of thesesprings 28 are arranged in the upper part of the core Hi and three inthe lower part.

The internal hollow defined conjointly by the core sections H and I2,has an equilateral hexagonal cross-section, and the block 22 has asmaller equilateral hexagonal cross-section separated from the walls ofsaid hollow by an intervening border gap 23 affording the necessaryspace for the collapse or contraction of the core It.

To hold the core sections H and 12 in assembled position shown in Fig.2, there is provided at one end of the core li! a core retaining headplate 25 shown in Fig. 1 having a circular or hexagonal face groove 26.the core sections l l and I2 have flanges 21 extending in the plategroove 26 and abutting the outer peripheral wall of said groove inlimiting expanded position of these core sections. The groove 26 is wideenough to permit radially inward collapse of the core Ill.

At its lower end, the core It seats on a retaining base member 28 shownin the form of a mold stool having a circular recess 30 for receivingthe lower end of saidcore. The outer peripheral wall of the recess 39 byits engagement with the outer peripheries of the core sections II andI2, limits radially outward movement of these sec: tions to the positionshown in Fig. 2, while permitting limited radially inward collapsingmovement of said sections under shrink pressure.

The metal core sections ill and l I are respece tively'hollowed andprovided with .end walls to The upper ends of stool 28 which also servesto seat the sectional core 18 centrally in the interior of the mold. Thea core l defines with the outer mold 35 an annular mold chamber 38 ofcircular or any desired cross-sectional configuration. e

The deposition of molten metal in the mold chamber 38 may be effected byany suitable manner, thus molten metal may be poured in the conventionalway from a ladle or other molten metal source or the metal may beproduced directly in mold chamber 38. For instance, a series ofcircumferentially spaced consumable electrodes 45 may extend into themold chamber 38 and be submerged in a blanket of floating flux 48 withthe lower ends of said electrodes spaced from the deposited molten metal4'1 by a gap. Current is discharged through the electrodes 45 and themetal 41 and across the intervening gap to progressively fuse the lowernds of said electrodes and produce the metal 41. Other ingredients toimpart to the metal 41 the desiredanalysis may be delivered to thefusing zone of the mold chamber 38. The electrodes 45 are fed and thecurrent supply adjusted so as to maintain a current discharg across thegap of substantially constant characteristics.

,During the fusing operations described, the mold is rotated slowly todistribute evenly the metal 41 deposited in the mold chamber 38 and toassure that the whole surface of the deposited metal is kept molten.This rotation of the mold may be effected in any suitable manner. Forexample, in the specific form shown, there is provided a turntable 58seating the mold stool 28 and carrying on its lower face a crown gearMeshing with this crown gear 5! is a bevel gear 52 driven from anysuitable source of power. This turntable 50 is supported by means ofthrust bearings 53 on a bearing post 55 extending upw wardly from afixed base 56. A shaft 51 depending from and rigid with the turntable 59is journalled in the post 55.

The core block 22 may extend downwardly through an opening in the moldstool 28 and seat on the turntable 58 for rotation therewith.

The body of metal 41 is grounded or otherwise connected to the currentdischarge circuit of the electrodes 45. This electrical connection maybe effected, for example, by means of a conductor ring or flange 68rigid with and depending from the turntable 50 and partially submergedin an annular mercury well 6|. This mercury well 61 is fixed to the post55 and connected to a lead 62 in the circuit of the electrodes 45. Thestool 28 and turntable 50 being of metal or other suitable electricalconductive material, the body of molten metal 41 will be connected tothe current discharge circuit of the electrodes 45.

The means for circulating a suitable cooling medium, as for examplewater, through various parts of the mold apparatus including the moldcore ID, desirably comprises an inlet pipe 65 leading into the base 56and connected to 'an annular recess 66 in a fixed distributing head 61.An outlet pipe 68 is connected to an annular recess I8 in thedistributing head 61, and extends outwardly through the base 56. Theshaft 51 has a central inlet duct 12 offset at its lower end forcommunication with the recess 66 and an outlet duct 13 offset at itslower end for communication with the recess '18. At its upper end, theinlet duct 12 extends through the turntable 58 and connects to the lowerend of a pipe 15 passing through the core block 22 and the upper coreretaining head plate 25. The upper end of this pipe 15 is connected to aheader 16 above the core [0. The cooling liquid is distributed from thisheader I6 to the core sections H and I2 by respective pipes 11. Sincethe core sections H and I2 are moved radially inwardly by the shrinkpressure of the cooling cast metal in the mold chamber 38, the pipes 11and 18 are desirably made of suitable yieldable material to permit thiscollapsing movement of the core sections.

The turntable 56 has an annular chamber 82 communicating by ducts withthe pipes 18 and also with theupper end of the outlet shaft duct 13.

The distributing system described can also be employed to circulatecooling liquid through the stool 28 and the. outer mold 35. For thatpurpose, the turntable 58 has a radial duct 85 connected at its innerend to the turntable duct 12 and at its outer end to one end of a pipe86. The other end of this pipe 86 leads into the upper inlet end of themold 35. The lower discharge end of the mold 35 is connected to one endof a pipe 81, the other end of which joins into the outer end of aradial duct 88 in the turntable 50. The inner end of this radial duct 88connects with the annular chamber 82 in the turntable 56.

Although one inlet pipe 86 and one discharge pipe 81. are shown for themold 35, it must be understood that any number of these pipes may beemployed suitably distributed and arranged to obtain the most effectivecooling of said mold.

To circulate cooling liquid through the turntable 58, said turntable hasa hollow 90 with one or more inlet connections 9i leading from the duct85, and one or more outlet connections 92 joined to pipe or pipes 81.

In the operation ofthe mold apparatus described, as the deposited metal4'! solidifies and cools, the resultant shrinkage of said metal causescompression of the core segments I l in a radially inward direction.This shrinkage pressure causes the core wedges 12 to slide radiallyinwardly against the resisting action of the springs 28, so that thecore segments H are moved radially inwardly and closer together. Thiscollapse of the core In permits it to be easily removed from the cooledcast metal and to be reused for subsequent casting operations. When thecore i8 is removed from the casting, the various sections thereof willbe restored to expanded condition under the biasing action of thesprings 28.

Although the core 10 of Fig. 2 has been shown in Fig. 1 as applied to aspecific mold apparatus, it must be understood that as far as certainaspects of the invention are concerned, this core l8 maybe employed inconnection with any other suitable mold apparatus.

In Fig. 3 is shown another form of collapsible mold core embodying thepresent invention. In this form, four main core sections Ha arequadrantly arranged and separated by wedge sections 12a. Each of thesemain core sections Ha has an outer circular conformation 13a and a pairof inner converging plane surfaces Ma On which slide the wedges l2a. Thecore sections Ha and I211 are hollowed to permit circulation of coolingliquid therethrough, and are shaped to conjointly define a continuousouter cylindrical surface in expanded position of said sections shown inFig. 3, and a central hollow of substantially square cross-section.Extending in this core hollow is a block 22a of substantially squarecross-section smaller in size than said hollow to define with the innerwalls of the core section a marginal gap 23a affording the necessaryspace for the collapsing movement of the core sections I la and I2a.Springs 20a have one end retained in respective recesses 2| a of thecore block 22a and the other end bearing against the bases of the wedgesl2a to urge these wedges radially outwardly. These springs 20a areprovided at the upper and lower sections of the core block 22a to affordthe necessary equilibrium. The recesses Zla are desirably arranged witheach pair of opposed recesses in a different plane from the otheradjacent pair of opposed recesses, so that the corners of the block 22awhere these recesses are disposed are not unduly weakened.

The core of Fig. 3 can be arranged in a mold as indicated in connectionwith the core [0 of Fig. 1 to shape the hollow of a casting. As the coresections Ila are pressed radially inwardly by the shrink pressure of thecooling casting, the wedges l2a are forced radially inwardly to causeapproachment of the main core sections lZa and collapse of the coreagainst the resisting action of the springs 20a.

As many changes can be made in the above apparatus, and many apparentlywidely difierent embodiments of this invention can be made withoutdeparting from the scope of the claims, it is intended that all mattercontained in the above description or shown in the accompanying drawingshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A mold core comprising a plurality of sections having outer circularsurfaces of the same radius, wedges spacing said sections andautomatically slidable radially inwardly upon the application ofshrinkage pressure of the cast material on the outer surfaces of saidsections, a block in the interior of said core, and spring means bearingon said block and urging said wedges radially outwardly.

2. A collapsible mold core comprising three similar substantiallysegmental circumferentially 6 arranged sections having outer circularsurfaces and inner plane substantially chordal surfaces, and a wedgebetween each adjoining pair of segmental sections having inclined planesurfaces seated on the inner chordal surfaces of said pair of adjoiningsegmental sections and slidable therealong to permit said sections tomove radially, the inclination of said wedge surfaces being such as toallow said wedges and said sections to move radially inwardly out ofmolding position upon application of compressive pressure by shrinkingcast metal on said circular surfaces, and means for yieldably resistingradially inward movement of said wedges.

3. A collapsible mold core comprising three similar substantiallysegmental circumferentially arranged metal sections hollowed to permitcirculation of a cooling medium therethrough, and having outer circularsurfaces and inner plane substantially chordal surfaces, a metal wedgebetween each adjoining pair of segmental sections hollowed to permitcirculation of a cooling medium therethrough, said wedge having inclinedplane surfaces seated on the inner chordal surfaces of said pair ofadjoining segmental sections and slidable therealong to permit saidsections to move radially, the inclination of said Wedge surfaces beingsuch as to cause said wedges to move radially inwardly upon applicationof compressive pressure on said circular surfaces, a block in theinterior space conjointly defined by said sections and said wedges, andsprings between said block and said wedges urging said wedges radiallyoutwardly.

4. A collapsible mold core comprising four similar quadrantly arrangedsections having outer circular surfaces respectively, and each having apair of converging inner plane surfaces extending away from itscorresponding curved surface, a wedge between each adjoining pair ofsections having inclined plane surfaces seated on the inner planesurfaces of said adjoining sections and slidable therealong to permitsaid sections to move radially, the inclination of said wedge surfacesbeing such as to allow said wedges and said sections to move radiallyinwardly out of molding position upon application of compressivepressure on said curved surfaces by shrinking cast metal, and springmeans urging said wedges radially outwardly.

ROBERT K. HOPKINS.

